1. Field of the Invention
The present invention relates to an ink container, an ink jet cartridge comprising an ink container and a printhead, and a process for manufacturing thereof.
2. Description of Related Art
A conventional ink supply device is disclosed, for example, in U.S. Pat. No. 4,771,295. The ink supply device is a head integrated-type ink cartridge having an ink tank to which a print head for jetting ink is integrally mounted. A porous member impregnated with the ink is provided inside the ink tank. The ink tank is provided with an ink supply passage for communication between the print head and the inside of the ink tank. A filter is disposed at one end (an ink supply opening) of the ink supply passage opening into the ink tank. Further, the ink tank is provided with an atmospheric air communication hole for communication between the inside of the ink tank and atmospheric air. The ink cartridge is mounted on a carriage. The carriage is reciprocated, and simultaneously the print head is driven to jet the ink, thereby printing desired data on printing paper.
Thus, the porous member impregnated with the ink is enclosed in the ink tank. As compared with an ink cartridge that has only the ink enclosed in the ink tank, the above-mentioned ink cartridge with an open-type ink supply mechanism effectively prevents the leakage of the ink from the atmospheric air communication hole owing to the ink retentivity of the porous member. Furthermore, the ink cartridge buffers a pressure fluctuation in the ink tank caused by movement of the ink due to acceleration upon reciprocation of the carriage.
However, the amount of ink that can be contained in the ink tank is obviously reduced by the presence of the porous member and this, together with that the print head and the ink tank are integral with each other in the head integrated-type ink cartridge, reduce the useful life of a print head, thus increasing a running cost.
Merely making the ink jet cartridge tank larger in size is not a satisfactory solution to problems associated with frequent replacement of the ink jet cartridge. The ink jet cartridges are generally mounted on the moving print carriage of the ink jet printer. Therefore, the larger the volume of the tank in the ink jet cartridge, the greater the amount of weight that is required to be moved by the printer carriage holding the ink jet cartridges.
The additional weight of the ink jet cartridges will cause significant demands on the motor that drives the printer carriage. Performance is also limited by heavier print carriages because a larger carriage inertia must be overcome at the two endpoints of carriage motion. At these locations, the carriage reverses direction to begin another pass over the media during the printing process. Increased carriage inertia increases the time required to reverse direction for a given drive motor size, and therefore can reduce print speed.
U.S. Pat. No. 5,839,595 discloses an ink container for storing the ink to be supplied to an ink jet head which comprises an ink container shell having a first and a second shell portion, a porous member disposed in the ink container, having a first and a second porous member portion which are disposed within the first and the second portion, respectively; wherein the first shell portion containing the first porous member portion is provided with an ink supplying portion, at which the ink container is connected to the ink jet head; and the second container shell portion containing the second porous member portion is provided with an air vent; and the first and the second container shell portion are joined to form the ink container.
The ink container disclosed in such a patent has an irregular shape to fit in the space within an ink jet printer and to maximize the useful volume of the container. The irregular shape of the ink container either would cause the formation of dead space if using a porous member of regular shape or would require the use of expensive process to cut the porous member to the desired shape. According to the patent specification, by dividing the ink container shell into portions with a simple shape, a porous member with a simple shape matching the simple shape of each of the divided portions can be inserted in the corresponding divided portion, therefore, eliminating the above mentioned problems.
However, the Applicant has noticed that the use of two porous member portions to be separately pressed before closing the container creates an interface zone wherein the material of the porous members are highly compressed. The pores of such a highly compressed zone are then reduced in size, and, accordingly, the capillary force is highly increased, by creating a zone of preferential distribution of the ink contained in the ink container. The proper flow of ink to the ink jet head is then altered, with consequent bad working of the print head and ink waste due to the retention of ink around the interface zone.
The use of different foam materials having different porosity within the an ink container is generally known. For example, U.S. Pat. No. 5,182,581 and U.S. Pat. No. 6,015,210, disclose the use of different foam materials to reduce leakage of ink through the vent hole or to improve the ink supply flow from the ink container to the printing head. However, the assembly of ink containers comprising different foam materials requires the use of complex and expensive manufacturing processes as well as an accurate control of the raw material and the process parameters to avoid zone of undesired preferential collection of ink.
The use of fibers as the porous member in ink supply devices is generally known in the art.
For example, U.S. Pat. No. 5,489,932 discloses an ink container for an ink jet print head having a main tank, in communication with the print head, filled with an compressed absorbent fibrous material which holds ink by capillary action, and an auxiliary tank, fixed alongside the main tank, sharing a wall with the main tank, and communicates with it by a channel at that end of the main tank which has the feed channel. The container can be refilled by inserting ink through an aperture into the auxiliary tank, from where it passes into the main tank by capillary action.
U.S. Pat. No. 5,453,771 discloses an ink container comprising one or more compressed fibers having different density, wherein the fibers are arranged in such a manner that they are closely filled in the ink container and have an increase of fiber densities as they approach the ink feed passage.
U.S. Pat. No. 6,877,847 discloses an ink container comprising two ink absorbing members made of polyolefin fibers disposed perpendicularly each other to avoid deformation of the main ink absorbing member.
However, none of the above mentioned references discloses or suggests the specific combination of features of the present invention in order to solve the above mentioned problems.